Abstract

Results are presented for observations of the a-type 2(02)-1(01)
transition of CH3NH2 (88.67 GHz) in the interstellar cloud Sgr B2. The
frequencies of the 2(02)-1(01) lines were measured in the laboratory,
and the observations were carried out using the NRAO 11-m telescope at
Kitt Peak. The observed line intensity is shown to confirm the
anomalously large population of the 2(02) level suggested by Fourikis et
al. (1974). Collisional excitation of CH3NH2 is analyzed, and it is
concluded that CH3NH2 molecules in Sgr B2 are excited by collision with
hydrogen molecules at particle densities of about 10,000 per cu cm. The
intensity of the a-type 2(02)-1(10) transition is shown to be
significantly increased by collision-pumped maser action.

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